System for controlling flow of a diluted sample and determining pollutants based on water content in engine exhaust emissions

Abstract

A system is provided in an exhaust emission sampling system for controlling a flow controller in order to compensate for the effects of changing water vapor content in a diluted sample having a predetermined dilution ratio. A water measuring device such as a relative humidity sensor generates a water vapor signal based on the amount of water vapor in the diluted sample. The water vapor signal is then processed within a control unit to obtain a value for the amount of water in the diluted sample. A control signal is generated by the control unit based on the amount of water vapor, flow rate of the exhaust emissions, and also, on the type of fuel used in the combustion process to control the flow controller which is, preferably, a mass flow controller. A second system is provided in an exhaust emission analyzing system for determining a final amount of pollutants also compensated for the effects of changing water vapor content in the exhaust emissions. The control unit not only processes the water vapor signal from the sensor to obtain a value for the amount of water vapor in the diluted sample as in the first embodiment, but also generates a correction factor based on the value. The correction factor is then utilized by a computer to calculate a final amount of the pollutants based on the correction factor and a preliminary amount of pollutants determined by analyzers of the exhaust emission analyzing system.

What is claimed is: 
     
       1. In an exhaust emission analyzing system including an exhaust emission analyzer for analyzing a diluted sample to obtain a preliminary amount of pollutants, a determining system for determining a final amount of pollutants compensated for the effects of changing water vapor content in exhaust emissions from an engine's combustion process, the determining system comprising: an exhaust emission sampler for preparing a diluted sample of exhaust emissions from an engine's combustion process;   a measuring device for generating a water vapor signal based on the amount of water vapor in the diluted sample;   a control unit for processing the water vapor signal to obtain a value for the amount of water vapor in the diluted sample and for generating a correction factor based on the value; and   a calculator for calculating the final amount of pollutants based on the correction factor and the preliminary amount of pollutants wherein the final amount of pollutants is compensated for the effects of changing water vapor content in the exhaust emissions wherein the control unit also generates a control signal based on the value to control the flow of the diluted sample.   
     
     
       2. The determining system as claimed in claim 1 wherein the control unit generates the control signal also based on the flow rate of the exhaust emissions. 
     
     
       3. The determining system as claimed in claim 2 wherein the control unit also generates the control signal based on the type of fuel used in the combustion process.